It's a sleeping pill, and unless you're sleep resistant you fall
asleep for up to 49 turns.

You become very fast (like a potion of speed or speed boots) for
200-209 turns.

Holy wafers will cure sickness and lycanthropy. (Note that if you are
a member of the Lycanthrope race, attempting to cure your lycanthropy
will not work. You will ``feel very bad!'', lose 3-5
points of
both strength and constitution, and have your HP reduced to a random
number between 1 and 5 if they were greater than 10 and otherwise to
1.) If you are Lawful, eating a holy wafer will also cause you to gain
20-39 HP. If you are Chaotic, you will lose 10-19 HP, but it will not
be fatal.

Two other edible items you may encounter are the Eye of the Beholder
and the Hand of Vecna. Eating them is really not a sensible thing to
do, and if you do it anyway, you will lose 150-199 HP.

This spoiler was written by Eva Myers (erm1001@cam.ac.uk).
If you have any comments, additions or corrections, please feel free
to email me.